class moblephone:
    battery = None
    # 私有成员__current_voltage
    __current_voltage = None

    def __init__(self, battery):
        self.battery = battery

    # 私有方法__keep_single_core
    def __keep_single_core(self):
        print("手机以单核模式运行")

    def Power_saving_mode(self):
        if self.battery <= 20:
            self.__current_voltage = 10
            print(f"电量低于20%,电压调整为{self.__current_voltage}")
            self.__keep_single_core()


phone1 = moblephone(10)
phone1.Power_saving_mode()